Space-time coding for the EDGE mobile radio system

The application of a space-time coding (STC) scheme using two transmit antennas in a GSM related TDMA mobile radio communications system is discussed. By way of example, we consider the simple space-time block code presented by S. Alamouti (see IEEE Journal on Selected Areas in Communications, vol.46, p.1451-8, 1998) in the presence of multipath environments, intersymbol interference (ISI) and additive white Gaussian noise (AWGN). Hard output Viterbi equalizers are used at the receiver site to combat the dispersive effects of ISI and multipath propagation. Computer simulation results for multi-tap block fading channels indicate a performance advantage of one diversity order over the conventional single transmit antenna scheme. In preliminary computer simulation results for the enhanced data rate for GSM evolution (EDGE) system, gains versus single antenna transmission schemes in the order of 2 dB (1.3 dB) at the block error rate 0.01 (0.1) have been obtained with ideal frequency hopping and the modulation and coding scheme MCS1 (GMSK modulation and a convolutional code with rate 0.53) in typical urban Rayleigh fading environments. The same gains in block error rate performance were achieved with a computationally simpler delay diversity scheme. Further work aims at completing a thorough performance comparison of different transmit diversity schemes for possible application in the EDGE system.